Dental instrument

ABSTRACT

A portable hand-piece dental instrument has a handle mounting a motor and battery. A speed changer is mounted in the handle. It removably mounts a chuck which in turn removably mounts a rotating dental tool.

1451 Nov. 19, 1974 United States Patent 1191 Copeland 11/1959 Klemas et a1. 11/1965 8800 222 555 lll DENTAL INSTRUMENT 3,220,039 Dayton et al. 3,435,477

[76] Inventor: John W. Copeland, 161 S. Oliver,

4/1969 M0yer................

Drapen et al.

Wichita, Kans. 67218 July 2, 1973 Appl. No.: 375,625

[22] Filed:

Primary ExaminerLouis G. Mancene Assistant Examiner-.l. Q. Lever Attorney, Agent, or FirmJohn Widdowson ABSTRACT A portable hand-piece dental instrument has a handle [52] US. 32/59, 32/DIG. 8

[51] Int. A6lc 3/06 [58] 32/59, 58; 15/28, 29

Field of Search mounting a motor and battery. A speed changer is mounted in the handle. lt removably mounts a chuck which in turn removably mounts a rotating dental tool.

References Cited UNITED STATES PATENTS 15/28 X 16 Claims, 18 Drawing Figures PATENTE; HOV I 91974 sum 10! 4 PATENTEL Maw @1914 3', 848.336

sum 20$ 4 BACKGROUND OF THE INVENTION The inventionis'related to portable rotary type selfcontained dental instruments of the type used to perform rotary work on teeth such as cleaning, polishing, or cutting. Numerous types of portable dental instruments are known in the prior art as operable for powering rotary type dental instruments to perform operations on teeth or dentures and the like. The prior art devices are constructed to use rotary dental-tools of a conventional structure such as a contra angle prophylaxis head mounting same in a rigid position relative to the hand held portion of the device. The prior art devices have miniature electric motors, such as a DC motor and a storage battery therein with the shaft of the motor directly connected with the shaft of the rotary dental tool. The prior art devices use a small high electric motor. Typically, the small high speed direct' current electric motor is used in the prior art devices; these motors typically have a relatively low operating torque at the operating speeds and stall when under a load such as in cutting, cleaning, and polishing operations. A direct current motor used for driving such prior art devices can be operated at speeds of approximately 12,000 revolutions per minute or more and require a working voltage of up to volts for such operation. Some prior art dental instruments utilize a remotely connected battery or source of power for the motor in the hand-piece. This type of portable device is somewhat portable; however, it is cumbersome in that the battery pack or whatever source of power is used must be carried by the person using the instrument and connected by a flexible cord or the like. Some of the prior art devices are provided with a variable resistor in the electrical circuit thereof between the battery and the motor for controlling the operating speed of the instrument. Controlling the speed of the instrument by changing the electrical power supplied to the motor reduces the output torque or output power characteristics of the motor as well as decreasing the operating speed of the motor and of the instrument. Reducing the speed of the instrument by this means is not desirable because this type of motor has inherently a relatively low torque and reducing the speed proportionally reduces the torque more.

SUMMARY OF THE INVENTION The dental instrument of this invention as disclosed herein includes several embodiments of the basic instrument invention; in all cases the structure includes a hand-piece with an electric motor mounted therin, a source of power mounted in the hand-piece,a rotary dental tool mount on the hand-piece for removably .mounting a rotary dental tool or the like in an operating position and further including a speed changing apparatusto mechanically change the operating speedof the output shaft to which the rotary dental tool or the like is attached relative to the operating speed of the motor. In one preferred specific embodiment, a dentalinstrument structure includes a motor and a battery mounted in the hand-piece in line in the hand-piece or handle, a rotatably mounted shaft connected by pulleys and a belt with the operating shaft of the motor, a mount for the rotary dental tool or the like to be driven from the rotatably mounted shaft, and with a control switch on the handle or hand-piece. 'In another preferred specific embodiment, adental instrument includes a motor and battery mounted in the hand-piece or handle in an in-line fashion, a rotatably mounted output shaft connected by a belt and pulleys with the motors of the output shaft, a mount for the rotatable dental tool or the like with a control switch mounted on the hand-piece and a second control switch mounted on the rotatable dental tool mount. In another preferred specific embodiment, a dental instrument structure includes a battery and a motor in a juxtapositional relation in the handle or'hand-piece, a rotatable output shaft connected bya belt and pulleys with the motors output shaft, a mount for the rotatable dental tool or the like, a battery recharging device and a control switch mounted on the hand-piece. In anotherpreferred specific embodiment a dental instrument structure includes a battery and a motor mounted in a handle or hand-piece, a rotatably mounted output shaft and a rotatably mounted intermediate shaft which 'is connected by a belt and pulleys with the motors output shaft and another belt and other pulleys connected with the rotatably mounted output shaft, a mount forthe rotatable dentaltool or the like anda control switch. Another preferred specific embodiment of the dental instrument structure includes a pair of power cells and a motor mounted in the handle or hand-piece, a rotatably mounted output shaft connected by a belt and pulleys with the motor output shaft, a mount for the rotatable dental tool or the like and a pair of control switches to connect one or bothof the power cells with the motor to provide for a two-speed operation.

One object of this invention is to provide a dental instrument structure overcoming the aforementioned disadvantages of the prior art devices.

Still, one other object of this invention is to provide a portable dental instrument structure having a mechanical speed changing apparatus between the powering motor of the instrument and the output shaft of the instrument.

Still, another object of this invention is to provide a dental instrument of a portable nature which has a mount for a rotatable dental tool or the like which will mount the contra angle piece or the like in a rigid position with the hand-pieceor handle of the dental instrument yet be rotatable by'finger pressure about its axis of support for operation of the dental instrument with a rotatable dental tool in a position about the axis of rotation of the mount.

Still, another object of this invention is to provide a dental instrument of a portable nature which has a rotatable dental tool mount with a control switch thereon operable to control the motor of the dental instrument by finger pressure.

Still, another object of this invention is to provide a dental instrument having a pair of power cells in the battery thereof connected 'to the motor thereof by separate control switches to provide a portable selfcontained dental instrument for mounting a rotatable dental tool or the like which has two operating speeds.

Yet, another object of this invention is to provide a dental instrument of a portable nature to provide a rotary power for operating a rotatable dental tool or the like which has a pulley mounted with the output shaft of the motor in the hand-piece, a second pulley mounted with the output shaft of the dental instrument with the pulleys being connected by an endless belt.

Yet, another object of this invention is to provide a dental instrument of a portable nature to provide rotational power for operating a rotatable dental tool or the like which has two sets of belts and pulleys connecting the output of a motor in the hand-piece or handle of the instrument through an intermediate shaft to the output shaft of the instrument for providing rotational motion to operate the contra angle piece or the like.

' Various other objects, advantages, and features of the invention will become apparent to those skilled in the art from the following discussion taken in conjunction with the accompanying drawings, in which:

DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view of an embodiment of the dental instrument having portions thereof cut away for clarity, with the motor and battery portions thereof shown in dashed lines,-the instrument having a straight shank type prophylaxis head rotatable dental tool;

FIG. 2 is a side elevation view of the dental instrument shown in FIG. 1 with the rotatable dental tool pivoted on the mount;

FIG. 3 is a cross-sectional view of the dental instrument shown in FIGS. 1 and 2, taken on line 33 of FIG. 2;

FIG. 4 is a schematic diagram of the electrical circuit of the dental instrument shown in FIG. 1;

FIG. 5 is a side elevation view of an embodiment of the dental instrument having a control switch on the tool mount, with portions thereof cut away for clarity, the dental instrument-having a contra angle prophylaxis head rotatable dental tool;

, FIG. 6 is a side elevation view of the dental instrument shown in FIG. 5;

indicated at 14 and shwon in FIGS. 9-ll. Another em- FIG. 7 is a top plan view of the dental instrument shown in FIGS. 5 and 6 without a rotatable dental tool;

FIG. 8 is a schematic diagram of the electrical circuit for the dental instrument shown in FIG. 5;

' FIG. 9 is a side elevation view of an embodiment of the dental instrument with the motor and the batteries thereof in juxtapositional relation as shown in dashed lines, the dental instrument having portions thereof cut away for clarity and fitted with a contra angle drill rotatable dental tool;

FIG. 10 is a side elevation view of the lower portion of the dental instrument shown in FIG. 9;

FIG. 11 is a top plan view of the dental instrument shown in FIG. 9 with the upper portion of the rotatable dental tool removed;

FIG. 12 is a sideelevation view of an embodiment of the dental instrument having four pulleys and an intermediate shaft connecting the motor and the dental instrument output shaft;

FIG. 13 is a side elevation view of the dental instrument shown in FIG. 12;

FIG. 14 is a cross-sectional elevation view taken longitudinally of the resilient coupler member used .to connect the output shaft of the dental instrument and the shaft of the rotatable dental tool;

FIG. 15 is a side elevation view of an embodiment of the dental instrument which is constructed for two speed operation and has a control switch on the mount FIG. 18 is a schematic diagram of the electrical circuit of the dental instrument shown in FIG. 15.

The following is a discussion and description of preferred specific embodiments of the dental instrument structure of this invention such being made with reference to the drawings, whereupon the same reference numerals are used to indicate the same or similar parts and/or structure. It is to be understood that such discussion and description is not to unduly limit the scope of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The dental instrument of this invention is shown and disclosed herein in five embodiments thereof which are closely related. An embodiment, (l), of the dental instrument is shown on Sheet 1 of the drawings and is generally indicated at 10. Another embodiment, (2), of the dental instrument, indicated generally at 12 and is shown'on Sheet 2 of the drawings inFlGS. 5-8. Another embodiment, (3), of the dental instrument of this invention is shown on Sheet 2 of the drawings generally bodiment, (4), of the dental instrument of this invention is shown on Sheet 3 of the drawings, generally indicated at 16, and shown in FIGS. 12 and 13. Another embodiment, (5), of the dental instrument of this invention is generally indicated at 18 and shown on Sheet 4 of the drawings.

The embodiment of the dental instrument, (1), shown on Sheet 1 of the drawings and generally indicated at 10 is the most basic of the several embodiments of the dental instrument of this invention. The dental instrument 10 includes a handle or hand-piece 20 with a chuck or mount 22 on the upper portion thereof to mount a rotary dental tool head such as the prophylaxis angle shown, and in' the handle or handpiece 20 a speed changing apparatus 26. The dental instrument 10 is shown with straight shank type prophylaxis angle tool mounted therewith to illustrate one of the multiplicity of rotary dental tools which can be operated with the dental instrument of this invention.

The handle or hand-piece 20 includes the motor 28 and battery 30 as shown in dashed lines within the handle-like enclosure portion 32 of the 2tructure. The upper portion of the handle or hand-piece 20 is a hollow enclosure 34 which encloses a speed changing apparatus 26 and supports a portion of the chuck or mount 22. The motor 28 has a shaft 36 extending therefrom into the hollow enclosure 34 with a pulley 38 mounted on its end portion. The dental instrument 10 has an output shaft 40 mounted as shown on bearings 42 and 44. A second pulley 46 is secured to the output shaft 40 and is connected by an endless belt 48 with the motor pulley 38. The bearings 44 and 42 are'preferably low-friction roller bearings or ball bearings which can be easilyrotated by the roller 28. As shown in FIGS. 1 and 3 the motor pulley 38 is substantially smaller than the second pulley 46 so the Output shaft 40 is rotated at a slower speed than the motor 28. A support for the hollow enclosure is attached to the side of the handle or hand-piece 20 as indicated at 43 to provide structural support for the output shaft and the hollow enclosure 34 on the end of the hand-piece 20. The ratio of the motor pulley 38 or drive pulley to the second pulley 46 or driven pulley is preferably in the range of 2:1 to 5:1 as such has been found in practice to provide output shaft rotating speeds suitable for prophylaxis, cutting and polishing of teeth, dentures, and the like.

The structure of the chuck or mount 22 of the dental instrument has an important feature of the dental instrument. The structure of the chuck or mount 22 allows a rotary dental tool 24 to be easily mounted with and removed from the dental instrument and rotated about the axis of the attachment of the tool to a convenient position and retained in that position. The'mount has a base 50 secured to the end 52 of the hollow enclosure 34 and a removable portion attachable to the rotatable dental tool. The base 50 has a flat portion secured to the end 52 and an upturned and exteriorly threaded portion 54 surrounding the instrument output shaft 40. The removable portion of the mount is attachable to the base 50. The removable portion of the mount 22 is indicated generally at 51 and is connectable between the base 50 and the rotary tool 24 and includes an inner threaded member 56, a sleeve 58 and an outerportion 60. The inner threaded member 56 is engagable with the exteriorly threaded portion 54 of the base 50. The sleeve 58 is expanded on its lower portion to encircle the inner threaded member 56 and is of a reduced size in a cylindrical portion 62 on its opposite end portion. The outer member 60 surrounds a lower portion of the sleeve 58 and on its upper portion 64 is spaced from the cylindrical portion 62 of the sleeve. Preferably, the inner threaded member 56, the

sleeve 58, and the outer member 60 of the removable portion of the mountare bonded together in a unit-like structure. The output shaft 40 has an upper end portion indicated at 66 which extends intothe mount 22. The rotary dental tool 24 has a shaft 68'through the center portion thereof by which rotary power is transmitted. The rotary tool 24 has a barrel-like structure 70 surrounding the shaft 68 with an enlarged collar 72 on its lower portion that slides over the cylindrical portion 62 of the sleeve 58 in an interference fit. The interference fit between the collar 72 and the cylindrical portion 62 of the mounts is sufficiently tight to retain the rotary dental tool 24 in position on the mount 22 yet allow it tobe rotatable on'the mount 22. The collar 72 slides on the cylindrical portion 62 so that the tool can be po-' sitioned as desired by finger pressure on the collar por- FIG. 14 on Sheet 3 of the drawings shows the resilient I coupler in detail. The resilient coupler is indicated generally at 77 and illustrates the preferred coupler used with all embodiments of this invention. The coupler 77 is preferably a resilient member of synthetic rubber or neoprene or other suitable material formed as shown.

Preferably, the coupler has a solid center portion 78 and similar end portions to receive the end portions of the shaft. The coupler as shown in FIG. 14 has a solid centerportion 78 and similarly constructed opposite end portions with the outer wall thereof indicated at 80 and the interior wall thereof indicated at 82. Preferably, in use the shafts of the tool and the dental instrument will extend into the coupler 77 with the ends of the shafts contactable or in a closely adjacent relation to the solid center portion 78. It is preferable, but not necessary that the coupler 77 be of a cylindrical con struction.

Power for the dental instrument 10 is provided by the battery 30. A control switch preferably mounted on a side portion of the handle-like enclosure portion 32 of the dental instrument. The control switch 75 is con nected as shown in the schematic diagram in FIG. 4 in a series relation with the motor 28 and the battery 30. The control switch 75 is preferably a push-button type switch to control on and off operation of the motor 28.

The motor 28 is preferably a direct current electric motor of a relatively high speed powered by the battery 30. The battery 30 is preferably permanently mounted in the hand-piece structure 20 and is of a rechargeable type. The lower end portion of the hand-piece enclosure 32 is preferably provided with an induction coil 79 connected with the battery 30 and usable-for recharging of the battery. The lower portion of the hand-piece enclosure 32 has a small cavity 80 used for support of the hand-piece on a mount or supporting stand. The induction coil battery recharging apparatus 79 is shown in a rectangle of dashed lines in FIG. 4 and illustrates the preferred apparatus for recharging the battery. It is to be understood that a recharging apparatus other than the reduction coil type can be used with the dental instrument 10. In practice it has been found that the induction coil type recharging apparatus provides a convenient and simple means of recharging the battery 30. It is to be noted that if desired the control switch 75 can be replaced by a rheostat with an on-off switch included to provide a variable speed control for the motor 28 without departing from the scope of the invention.

In practice'in using the dental instrument 10 of this invention, such has been accomplished by the use of a small electric motor of the general size used in portable electric toothbrushes and with a battery of a similar type. In this practice of the invention the motor has a rotation speed of approximately 8,000 to 10,000 revolutions per minute and the output shaft of the dental instrument has a rotating speed-of approximately 400 revolutions per minute to 600 revolutions per minute which has proven to be adequate for dental prophylaxis. Typically, rotating tool speeds for dental prophylaxis are in the range of 400 revolutions per minute to 5,000 revolutions per minute. Rotating tool speeds for cutting and polishing operations on teeth and the like are in the range of 5,000 revolutions per minute to 30,000 revolutions per minute. In the use of the dental instrument 10 for prophylaxis the speed changing apparatus 26 enables the motor 28 to operate at a very high rent electric motor, increasing or decreasing the voltage and power capacity of the battery will cause the motor to rotate at a higher speed or a lower speed thereby raising or lowering the output rotating speed of the tool. The battery used with the dental instrument can be of a voltage andpower capacity to sustain operation of the motor at the upper speed range requirement for the use for which the instrument is intended, such as drilling and a rheostat or variable resistor used to reduce the tool speed as required or as desired. It is to be noted that the dental instrument can be provided with means to modify the capacity of the battery such as by adding or removing individual power cells in the battery. The dental instrument 10 can be constructed to receive and hold a single replaceable dry cell or a plurality of replaceable dry cells. I

The dental instrument 10 of this invention is completely portable and can easily be held in a persons hand. The dental instrument 10 can be grasped and operated between the thumb and the fingers either in the palm of the hand or above the hand. Positioning of the control switch 75 on the side of the handle or handpiece 'makes it conveniently pressable as the dental instrument is grasped and held. The handle or handpiece 20 is constructed such that it can be held in the palm of the hand by the fingers and the control switch 75 can be operated by the thumb which is convenient 'and safe considering some dental operations and procedures require quick motions and relatively rapid reflex action on the part of the dentist.

Another embodiment, (2), of the dental instrument of this invention is indicated at 12 and is shown on Sheet 2 of the drawings in FIGS. 5-8 thereof. The dental instrument 12 of this embodiment of this invention is basically similar to the hereinbefore described first embodiment, (1), of thedental instrument of this invention and further includes a second control switch on the tool mount portion of the structure in addition to the control switch on the hand-piece portion of the structure. The dental instrument 12 includes a handle or hand-piece 90 enclosing the motor and battery in an interior portion thereof on one end and on its opposite end portion a hollow enclosure for the speed changing apparatus 92. The rotatable tool mount 94 or chuck is I on the upper portion of the handle or hand-piece 90;

it has a control switch thereon and is adapted to removably engage in a rotatable operating position the rotatable dental tool such as the contra angle prophylaxis tool shown. The dental instrument 12 is constructed so that it can be held in the hand and operated by the control switch on the side of the handle or hand-piece 90 or held in the hand and operated by the control switch on mount 94. The control switch on the mount 94 makes it possible to support the dental instrument 12 in a balanced condition as may be comfortable or necessary for precision movements of the rotary dental tool or for comfort of the user.

The hand-piece or handle 90 is provided with an enclosure portion 97 which encloses a motor 98, a battery 100 and preferably an induction coil recharging device 102 as illustrated in the schematic diagram in FIG. 8. The control switch 103 is provided on the side of the handle-like enclosure 97 to control the motor 98. The motor 98, battery 100, and recharging apparatus 102 are preferably constructed similar to that shown in FIGS. 1 and 2 and described in conjunction with the first described embodiment, (1). The speed changing apparatus 92 connects the motor 98 to an output shaft for the dental instrument. The motor 98 has an output shaft 104 with a pulley 106 secured thereto and positioned in the hollow portion of the handpiece adjacent to the end indicated at l08.-The output shaft of the dental instrument is indicated at 110 and is supported by the roller bearings 112 and 114 in the hand-piece end enclosure. A pulley 116 is secured to the rotatably mounted output shaft 110 and connected by a belt 118 with the motor pulley 106. The output shaft extends from the handle or hand-piece 90 as shown and into a portion of the mount 94.

The mount 94 or chuck has a base member 120 secured to the end 108 and a removable portion indicated generally at 119. The base 121 includes an upwardly extending and externally threaded center portion 121 on which a removable portion of the mount 94 is attachable. The mount or chuck removable portion 119 includes an internally threaded member 122 engagable with the externally threaded portion 121 of the mount base 120, a sleeve 124 expanded on its lower end portion to fit over the threaded member 122 cylindrical on its upper end portion 126 and an outer member 128 expanded on its lower portion 130 around the sleeve 124 and internally cylindrical on its upper portion 132 and having the second control switch 134 mounted on its upper portion 132. The interior of the v laxis tool and has a barrel portion 138 with a shaft 140 centrally disposed therein, with the barrel 138 being used to connect the tool and support the tool with a powering device. The cylindrical sleeve 126 fits inside of the barrel 138 as shown in an interference fit which is sufficiently tight to retain the tool in position yet allow for rotation of the barrel 138 relative to the sleeve 126 and the chuck or mount 94 by finger pressure. The upper end of the dental instrument output shaft 110 is indicated at 142 and extends into the interior of the mount94. A resilient coupler member 144 connects the output shaft end portion 142 with the shaft 140 of the rotary dental tool 96. The resilient coupler 144 is shown in detail in FIG. 14 and generally indicated therein at 77. The coupler 144 transmits rotary motion from the speed changing-apparatus 92 to the rotary tool 96.

The electrical system of the dental instrument 12 is shown in the schematic diagram in FIG. 8 and includes a set of contacts to electrically connect the control switch 134 on the mount 94 with the motor 98 and battery 100. The structure of the set of contacts includes a contact support block 146 secuqed to the dnd of the hand-piece enclosure end 108 adjacent to the base 120, a set of contacts 148 and 150 on the upper portion-of the block 146, and a cooperating pair of contacts 152 and 154 secured to the outer flange-like expanded portion 130 of the removable mount portion 1 19. The control switch 134 is mounted in the wall of the upper mount portion 132 with a button 135 on the exterior of the outer surface. The wires from the control switch 134 are located in the removable portion of the mount 128 as shown in FIG. 5. When the removable portion of the mount is screwed onto the mount base 120 the contacts 152 and 154 are brought into cooperating contact with the contacts 148 and 150 on the mount block 146. Referring to the schematic diagram of FIG. 8 the switches 103 and 134 are in a parallel relation so closing of either of the switches will operate the motor hereinbefore described being in conjunction with the first embodiment, (l), and functionally operate the same. It is to be understood that the speed changing apparatus 92 shown in FIG. is a speed reducing apparatus that can be constructed with the pulleys thereof sized so as to provide a speed increase, if desired, for the output shaft relative to the motor shaft.

In practice and in use of this dental instrument 12, it has been found that the second control switch 134 on the mount 94 is a useful and convenient feature. A structure of the mount'94 is sized such that it can be comfortably grasped by the fingers with the hand-piece 90 resting on the portion of the hand between the thumb and forefinger with the push-button 135 on the second control switch 134 operated by the thumb or the forefinger. The structure of the hand-piece 90 is such that the control switch 103 can be operated with a thumb or a finger with the hand-piece positioned generally between the thumb and thefingers and used similar to the dental instrument of the first described embodiment, (l).

Another embodiment, (3), of the dental instrument of this invention is shown on Sheet 2 of the drawings in FIGS. 9, l0 and 11 and generally indicated at 14 therein. The dental instrument 14 includes a handle or hand-piece 160 with a speed changing apparatus 162 in a hollow portion thereof, a chuck or mount 164 on the end portion of the handle or hand-piece 160 to removably mount a rotary dental tool 166. The rotary dental tool 166 shown in FIG. 9 has a contra angle drill tool mounted thereon which is illustrative of the types of rotary dental tools-usable with the dental instrument 14 and the other embodiments of the dental instrument of this invention. The hand-piece or handle 160 is an enclosure as shown in FIGS. 9, 10 and 11 and encloses a battery having a pair of cells 170 and 172 shown in dashed lines, a motor 174 and a battery recharging apparatus 176. The end of the handle or hand-piece 160 which encloses the speed changing apparatus 162 is a hollow enclosure portion with an end member 178'to which a portion of the chuck or mount 164 is secured. The shape of the hand-piece enclosure 168 can be seen in the combination of the views of the dental instrument 14 shown in FIGS. 9, 10 and 11 as generally cormounted dental instrument output shaft 184 supported in bearings 186 and 188 in the structure of the handpiece enclosure 168 with a second pulley 190 secured to the shaft 184 and a belt 192 therearound the pulleys. The speed changing apparatus 162 as shown has the first pulley or drive pulley 180 larger in diameter with the second pulley 190 or the driven pulley so the rotational speed of the output shaft 184 is greater than the rotational speed of the motor shaft 182 during operation. It is to be noted that the speed changing apparatus 162 can be constructed with the first pulley 180 smaller than the second pulley 190 so the rotational speed of the output shaft 184 is slower than the rotational speed of the motor shaft 182.

The mount or chuck 164 of the dental instrument 14 has a base 194 secured to the handle or hand'piece end 178 with a central upwardly extending and exteriorly threaded portion 196 therearound the output shaft 184. The removable portion of the chuck or mount 164 is indicated at 198 and includes an interiorly threaded inner member 200, a sleeve 202 expanded on its lower end portion around the inner member 200 with a cylindrical upper portion 204, and an outer member 206 therearound the exterior of the sleeve 202. Preferably, the outer member 206, the sleeve 202 and the inner member 200 are bonded together by an adhesive material as a unitary structure. The inner member 200 is threadedly attachable to the base central upright portion 196 providing for removably mounting the mount portion 198 with the hand-piece. The rotary dental tool 166 has a barrel portion 208 with the tool shaft 210 centrally disposed therein. The lower portion of the barrel 208 slips over the exterior of the cylindrical sleeve 204 in an interference fit. The interference fit between the barrel 208 of the rotary dental tool 166 and the cylindrical portion 204 of the sleeve 202 is an important feature of the chuck or mount 164 in that the fit is sufficiently tight to hold the rotary tool 166 in a rigid position relative to the chuck or mount 164 yet its not so rigid as to prevent rotation of the tool barrel 208 by finger pressure as desired. The particular mounting of the rotary tool 166 enables it to be rotated about the barrel 208 on the cylindrical sleeve portion 204 to any desired position. A resilient coupler member 212 connects the tool shaft 210 and the upper end portion 214 of the dental instrument output shaft 184. The resilient coupler member 212 is shown in detail in FIG. 14, generally indicated at 77 therein and preferably the same as described hereinbefore. The upper inner portion of the outer mount portion 206 is spaced from the cylindrical portion of the sleeve 204 as shown.

The electrical circuit for the dental instrument 14 is substantially the same as the electrical circuit shown in FIG. 4 wherein the battery is connected in series with a control switch and the motor and a recharging apparatus is connected with the battery. The battery for the dental instrument 14 consists of two power cells 170 and 172 connected in a series connection. The battery recharging apparatus as indicated at 176 in FIG. 9 is provided with a jack 216 for connecting same with an external source of electrical power, preferably com mon household power of 1 l5 voltsaltemating currents. The battery recharging apparatus 1767is contained in the hand-piece and permanently connected with the battery cells and 172. A plug and cord, (not shown) are used to connect the jack 216 to a source of electrical power for recharging the battery. The control switch for the electrical circuit is preferably mounted on the side of the hand-piece 160 and is indicated at 218 on an extended portion of theenclosure 168. Pref erably, the control switch 218 is positioned such that it can be easily contacted and pressed by the thumb or a finger when the dental instrument 14 is held in the hand. It is to be understood that the dental instrument 14 can be constructed with a single rechargeable battery having multiple cells, or it can be constructed having multiple batteries to provide the electrical power.

' Another embodiment, (4), of the dental, instrument of this invention is shown on Sheet 3 of the drawings in FIG. 12 and FIG. 11.3 and indicated generally at 16. The dental instrument 16 is basically similar to the hereinbefore described embodiments of the dental instrument of this invention and includes a hand-piece or handle 220, a speed changing apparatus 222 and rotary dental tool chuck or mount 224. The hand-piece or handle (3). Only the stationary base portion of the chuck or mount 224 is shown in FIGS. 12 and 13. The removable portion of the chuck or mount 224 is the same as that shown in FIGS. 1, 2, 9 and 10 and is omitted in FIGS. 12 and 13 to more clearly show the stationary portion of themount.

The hand-piece or handle 220 has a handle-like enclosure 228 enclosing the direct current electrical motor and the battery and having mounted on the exterior thereof thecontrol switch 230. Preferably, the

hand-piece or handle 220 has a battery recharging apparatus of the induction coil type as shown and described hereinbefore in conjunction with the first described embodiment, (l), of the dental instrument of this invention. Preferably, the enclosure 228 is a crosssectional annular structure with elongated and tapered side walls. The speed changing apparatus 222 is mounted in a hollow enclosure end portion of the handpiece or handle 220 and is indicated generally at- 232. The hollow portion of the enclosure 232 is shown removably mounted with the handle-like portion of the I hand-piece 260. The removable portion of the enclosure has lugs 234 and 236 extending therefrom which are securable with the sides of the hand-piece by bolts or the like as shown. The hollow enclosure portion 232 has an end portion 238 to which the mount base 240 is secured. Sides of the hollow enclosure portion 232 enclose and support the structure of the speed changing apparatus 222. The stationary portion of mount 224 has a base 240 secured to the hollow enclosure end 238 and an upwardly extending and exteriorly threaded center portion used for threadedly attaching the removable portion of the mount. The removable portion of the mount 234 being structurally the same as the removable portion of the mount shown in FIGS. 1, 2, 9, and 10. I

The speed changing apparatus 222 is comprised of two connected stages, a primary stage from the motor and a secondary stage to the dental instrument output shaft. In the primary stage the motor output shaft 224 has a pulley 246 secured thereto, a rotatably mounted intermediate shaft 248 with a second pulley 250 secured thereto and a belt 252 therearound the first pulley or motor rotated pulley 246 and the second pulley 250. The intermediate shaft 248 is preferably mounted with substantially friction-free bearings such as roller bearings, not shown in the drawings. The secondary portion of the speed changing apparatus 222 has a third pulley 252 secured to the intermediate shaft 248, a

dental instrument output shaft 254 rotatably mounted with the enclosure end 238, a fourth pulley 256 secured to the output shaft 254 and a belt 258 therearound the third pulley 252 and the fourth pulley 256. The primary and secondary stages of the speed changing apparatus is so constructed that rotation of the motor output shaft 244 causes the intermediate shaft 248 to be rotated and the dental instrument output shaft 254 also to be rotated. Preferably, the dental instrument output shaft is mounted with substantially friction-free bearings such as roller bearings, not shown in the drawings. The end of the dental instrument output shaft 254 extends above the mount base 240 and is indicated at 255. In the speed changing apparatus 232 shown in FIGS. 12 and 13 the first, second, and third pulleys 246, 250 and 252, respectively, are substantially the same diameter and the fourth pulley 256 is substantially larger. In this instance the speed ratio between the motor output shaft 244 and the dental instrument output shaft 254 causes the dental instrument output shaft 254 to rotate at a slower speed than the motor shaft 244. It is to be understood that the sizes of the several pulleys 246, 250, 252, and 256 of the speed changing apparatus of this dental instrument can be varied in size to obtain any desired speed ratio between the motor output shaft I and the dental instrument output shaft which would cause the effective speed of the dental instrument output shaft 254 to be lesser than or greater than the speed of the motor shaft 244. The primary and secondary portions of the speed changing apparatus can be fitted with pulleys of suitable selected sizes to substantially increase or decrease the rotation ratio of the output shaft relative to the input shaft or motor shaft as desired by the user. The compound type speed changing apparatus 222 of this embodiment, (4), of this invention by virtue of its two stages is particularly adapted for using a relatively high speed motor and by selecting the size ratio of the pulleys obtaining an extremely high operating speed or an operating speed slower than that of the motor. Additionally, the speed changing appara tus 222 is adapted for use with a motor of a low or nominal speed and by selecting the size ratio of the pulleys obtaining a relatively high instrument output speed or a relatively low instrument output speed. The compound type speed changing apparatus of this embodiment, (4), of this invention provides a compact speed changing apparatus capable of providing a substantial speed ratio between the dental instrument motor and the dental instrument output shaft.

The electrical system of the dental instrument 16 is preferably similar to the electrical system shown and described in conjunction with the first embodiment, (l), of this invention and includes a motor, a battery, and the control switch 230 connected in a series rela tion and having an induction coil type recharging apparatus connected with the battery. The schematic diagram of this preferred electrical circuit is shown in FIG. 4. It is to be noted that the electrical system of the dental instrument 16 can be constructed with a battery having multiple cells of a rechargeable nature and it can be constructed having multiple cells of a replaceable type as previously discussed. It is also to be noted that the control switch 230 can be substituted for a rheostat type switch to connect a resistor or load in the electrical circuit thereby providing for a variable speed control for the motor.

Another embodiment, (5), of the dental instrument of this invention is shown on Sheet 4 of the drawings, in FIGS. 15-18 and generally indicated at 18. The dental instrument 18 includes a handle or hand-piece 262 with the speed changing apparatus 262 in a hollow end portion thereof, a chuck or mount 264 on the end of i having two separate power cells connectable with the motor individually or in series to provide a two-speed operation of the dental instrument. Control for the dental instrument 18 is accomplished by control switches on the rotatable dental tool mount or chuck 264. The hand-piece orhandle 260 has an enclosure encasing the motor, the battery, the speed changing apparatus 262, and a switch which is part of the electrical circuit. The enclosure 270 of the handle or hand-piece 260 has a hollow end portion to enclose a speed. changing apparatus. The enclosure has an end 272 that forms a support for the dental instrument output shaft and for the fixed or stationary portion of the mount 264.

The speed changing apparatus is enclosed in the hollow end portion of the hand-piece 260 as shown in FIG. 15. The speed changing apparatus 262 includes a first pulley 274 secured to the motor output shaft 276, a rotatably mounted dental instrument output shaft 278 with a second pulley 280 secured thereto and a belt 282 therearound the first pulley 274 or drive pulley and the second pulley 280 or driven pulley. The dental instrument output shaft 278 is preferably supported by low friction-free bearings, one of which is shown and indicated at 284. The outer end of the shaft 278 is indicated at 286 and extends above the base portion of the mount 264. The rotatable dental tool mount 264 includes a base 288 secured to the hand-piece enclosure end 272 and a removable portion indicated generally at 292. The base member 288 has an upwardly extended and exteriorly threaded portion 290 therearound the dental instrument output shaft 278. The removable portion 292 has an internally threaded inner member 294 removably engagable with the upwardly extended base portion 290, a sleeve 296 expanded onthe lower portionaround the inner member 294 and an outer member 298 therearound the sleeve 296. The sleeve 296 has an elongated cylindrical upper portion 300 within the upper portion of the mount outer portion 298. The rotatable dental tool 266 has an outer barrellike portion 302 enclosing a shaft 304. The interior of the rotatable tool barrel 302 is sized to slip over the cylindrical sleeve portion 300 in an interference fit. The interference fit between the tool barrel 302 and the sleeve 300 has an important feature of the dental instrument 18 in that it is sufficiently tight to retain the rotatable dental tool 266; however, it is sufficiently loose to permit rotation of the tool barrel about the sleeve 300 by finger pressure on the two exposed portions of the dental tool 266. Preferably, there is a space between the exterior of the dental tool barrel 302 in the interior of the-mount upper portion 398 as indicated at 306 to faciliate easy insertion of the tool into the mount and to provide a mount which will accommodate rotary dental tools of varying exterior of various dimensions. With the rotatable tool 266 in place as shown in FIG. a resilient coupler member 303 connects the dental instrument output shaft on its outer end portion 287 with the tool shaft 304. The resilient coupler member is the type lof coupler member shown in FIG. 14 and generally indicated therein at 77. The mount or chuck 264 supports the control switches for the motor and contacts for connecting the switches in the electrical circuit of the dental instrument.

The electrical circuit of the dental instrument 18 is shown in FIG. 18 and includes a battery with two cells, one indicated at 310 andone indicated at 312. The electrical system shown is constructed to connect the battery cell 310 to the motor 314 or in the alternative connect the battery cells 310 and 312 in series and with the motor 314 as well as connecting the battery cells and series for recharging thereof. A first control switch or a low speed control switch 316 is connected between the battery 310 and the motor 314. Two pairs of contacts 318 and 320 join the switch 316 with the circuit. The contacts 318 and 320 have one contact of each set secured to the removable mount portion 292 and the matching contact of each set on a contact base 322 that is secured to the hand-piece enclosure 270. A second control switch or high speed control switch is indicated at 324 and is connected between the second battery cell 312 and the first battery cell 310. Two sets of pairs of contacts 326 and 328 connect the second control switch 324 in the circuit. The contact sets 326 and 328 also have one contact each on the mount 292 and one contact each secured to the contact base 322. FIG. 15 shows in detail the structure of a set of contacts which is representative of the several set-s of contacts in the electrical circuit of this dental instrument 18. The upper contact is indicated at 331 and is secured to the removable mount portion 292. The lower contact 330 is secured to the contact base member 322 on the enclosure end 272. Each of the sets of contacts is connected preferably by wires in the electrical circuit. Referring to the schematic diagram of FIG. 18 a third switch indicated at 332 is provided in the circuit and functions to control operation of the circuit between a first condition allowing the motor 314 to operate and a second condition for recharging of the battery cells. The switch 332 is a double throw double pole switch connected as shown with the high speed control switch 324, the battery cells and the motor 314. One side of the switch 332 bridges the high speed control switch 324; the other side of the switch 332 connects the negative pole of the battery cell 310 and the motor 314. In a condition to running the motor 314 the switch 332 is thrown to the right as shown in the drawing for connecting the negative pole of the battery cell 310 and the motor 314. When set in a condition for recharging the battery the switch 322 is thrown to the left as it appears in the drawings bridging the high speed control switch 324 and connecting the negative pole of the battery cell 312 with the positive pole of the battery cell 310. Connections for recharging the battery are made at the positive pole of the battery cell 312 and the negative pole of the battery cell 310 as indicated. Contacts 330 and 334 and 336 are provided on the positive connection and negative connection, respectively. The contacts 334 and 336 extend from the enclosure end 338 on what is shown as the lower portion of the hand-piece 260. The control switch 322 is preferably mounted on a side portion of a hand-piece 260 as shown in FIGS. 15-17. The base or recharger stand 268 is shown in FIGS. 16 with portions removed with the dental instrument 18 therein. The stand has a socket portion in which the hand-piece 260 is placed in an upright position with the hand-piece end 338 being on the bottom.

the base or recharging stand 268 can be varied from the structure shown as desired by the user with the important feature of the structure being a support for the hand-piece 260 and contacts to cooperatively engage ,-the matching contacts on the hand-piece 260 for recharging of the battery. For recharging of the dental instrument battery the control switch 322 must be posit'ioned as described to connect the cells of the battery in a series relation with the contacts 334 and 336. It is to be noted that the structure of the recharging stand 268 can be constructed so the dental instrument l8 cannot be inserted without the switch 332 being in the proper position. The structure of the dental instrument 18 with the contacts 334 and 336 on the bottom thereof provides a hand-piece structure which is well suited to the drop-in type support of the dental instrument by the base or stand 268 or a similar suitable supporting structure. It is to be noted that once the handpiece 260 is removed and the control switch 332 is set for the running condition and electrical connection between contacts 334 and 336 will not short the battery so as to discharge same.

In the manufacture of the dental instrument structure of this invention, it is obvious that the several embodiments ofthe dental instrument of this invention are adequately and properly constructed to achieve the end product. The manufacture of the handle or hand-piece portions of the structure can obviously be accomplished by processes similar to those currently used in the art of manufacturing portable electrically powered toothbrushes as the structures are of a generally similar nature. The speed reducing apparatus portion of the I dental instrument structure presents no difficulty in manufacture as the current art is well developed in the production of small belts, pulleys, and the like as exemplified by the structure of small portable tape recorders and the like. The mount or chuck portion of the several embodiments of the dental instruments of this invention are constructed generally similar and can be easily manufactured by molding techniques common in the art of plastic and metal bonded structures. The dental instrument of this invention is adapted to use the standard size and popular construction of rotatable dental tools such as the prophylaxis angles, drills and the like.

In the use and operation of the dental instrument of this invention'it is seen that same provides a portable power source for operating rotatable dental tools which is superior to the prior art. The speed changing apparatus of the dental instrument makes the best available use of the power produced by the small direct current electric motor. The speed changing apparatus of the dental instrument can be constructed to increase or decrease the output speed of the dental instrument relative to the operational speed of the motor thereof which is a desirable feature and which will enable a manufacturer to produce more or less standard handpieces or handles modifying only the speed changing apparatus pulleys to produce dental instruments of a high speed capability or a low speed capability without substantially altering the manufacturing process. The several embodiments of the dental instrument of this invention provide various conveniences for the dentist which are not available on current art dental instruments. These advantages are namely the on-off control switches on the mount portion of the dental instrument and the two-speed operation capability of the dental instrument. Positioning the control switches on the mount and on the sides of the hand-piece makes the dental instrument easy to grasp and control. ln practice it has been found that positioning of the control switches on the side of the hand-piece and on the mount do not detract from the reflexes of the user in performing dental operations. It is to be noted that the dental instrument of this invention allows a dentist to assume a standing position with both feet flat on the floor while performing dental operations and thereby allowing the dentist to assume a more comfortable position than possible with foot switch controlled dental instruments.

As will become apparent from the foregoing description of the applicants dental instrument structure, relatively inexpensive and simple means are being shown to provide a portable dental instrument which is extremely convenient to use. The dental instrument structure is simple to use, economical to manufacture, attractive in appearance and is adapted to use standard rotary dental tools. The dental instrument structure has a speed changing apparatus to make the best use of available torquefrom the small D.C. electric motor. The mount of the dental instrument is adapted to removably mount conventional rotatable dental tools in a manner which will allow them to be rotated by finger pressure and to operate in any position of rotation about the axis of the mount.

While the invention has been described in conjunction with the preferred specific embodiments thereof, it will be understood that this description is intended to illustrate and not to limit the scope of the invention, which is defined by the following claims.

I claim:

1. A portable dental instrument, comprising:

a. a hollow handle,

b. an electric motor mounted in said handle, said electric motor having a power output shaft,

c. means to power said electric motor mounted in said handle and connected to said motor,

(1. speed changing means mounted on said handle and connected to said electric motor output shaft, said speed changing means, having an output shaft, and

e. rotary dental tool mounting means for removably mounting a rotary dental tool in operating position, mounted on said speed changing means, and connected to said rotary dental tool when mounted to change the operating speed of said tool relative the operating speed of said motor, said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool and a sleeve member slidably engagable with said rotary dental tool and mounting said tool by friction pressure such that said tool is rotatable on said sleeve by fingerpressure.

2. The dental instrument of claim 1, wherein: a. said speed changing means has means to operate said rotary dental tool at a rotating speed different from the rotating speed of said motor output shaft,

b. said means to power has a rechargeable battery and means to connect said battery with a battery charger means for recharging same said battery, and i c. a motor control switch is mounted with said handpiece and connected with said motor and said battery.

3. A dental instrument of claim 2, wherein:

a. said speed changing means has a first pulley secured to said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys.

4. The dental instrument of claim 3, wherein:

a. said sleeve member is removably mountable with said handle,

b. said sleeve member is slidably engagable in an annular mount portion of said rotary dental tool,

c. said motor is mounted in said handle in a position generally aligning with said battery,

d. said means to connect said battery with a battery charger is an induction coil means, and

e. said speed changing means is constructed and adapted to operate said rotary dental tool at a rotating speed lesser than the rotating speed of said motor, with said second pulley being larger than said first pulley.

5. The dental instrument of claim 1, wherein:

a. said speed changing means has means to rotate said rotary dental tool at a speed different than the rotating speed of said motor output shaft,

b. said means to power has a rechargable battery and means to connect said battery with a battery charger means for recharging, and

c. said means'to power has a pair of parallely connected control switches, one switch mounted with said handle and a second switch mounted with said rotary dental tool mount means.

6. The dental instrument of claim 5, wherein:

a. said speed changing means has a first pulley secured said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys,

b. said mount means has means to connect said second switch with said motor and said battery, and

c. said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool, and a sleeve member slidably engagable with said rotary dental tool mounting said tool by friction pressure such that said tool is rotatable on said sleeve by finger pressure.

7. The dental instrument of claim 6, wherein:

a. said sleeve member is. removably mountable with said handle,

- b. said sleeve member is of a diameter to be slidably engagable in an annular portion of said rotary dental tool,

c. said mount means has an outer member secured to second pair of contacts secured to said outer member, said pairs of contacts being cooperatively engagable when said outer member is mounted with said handle.

8. The dental instrument of claim 3, wherein:

a. said sleeve member is removably mountable with said handle,

b. said sleeve member is of a size to be slidably engagable in an annular mount portion of said rotary dental tool,

c. said motor is mounted in said handle in a juxtapositional relation to said battery, and

d. said output shaft is positioned with said rotatable axis thereof in a spaced relation to said motor and generally aligning with said battery.

9. The dental instrument of claim 8, wherein:

a. said output shaft is positioned with said rotatable axis parallel to said motor and in the space adjacent an end portion of said battery, and

b. said means to power has a battery recharger means mounted in said handle connected to said battery and connectable to a source of electrical power.

10. The dental instrument of claim 2, wherein said speed changing means has a first pulley secured to said motor output shaft, a rotatably mounted intermediate shaft having a second pulley and a third pulley secured therewith, said output shaft having a forth pulley secured therewith, a first drive belt therearound said first pulley and said second pulley and a second drive belt around said third pulley and said fourth pulley.

11. The dental instrument of claim 10, wherein:

a. said intermediate shaft is mounted in a spacedrelation to said motor, and

b. said output shaft is mounted in a spaced relation to said intermediate shaft and generally aligning with said motor.

12. The dental instrument of claim 1, wherein:

a. said speed changing means has means to rotate said rotary dental tool at a speed different than the rotating speed of said motor output shaft,

b. said means to power has a rechargable battery and means to connect said battery with a battery charger means for recharging,

c. said battery has a first power cell and a second power cell, and

d. said means to power has a first switch means con nected to said first power cell and to said motor and a second switch means connected to said first power cell, to said second power cell and to said motor in a series relation.

13. The dental instrument of claim 12, wherein:

a. said speed changing means has a first pulley secured to said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys,

b. said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool, and a sleeve member slidably engagable with said rotary dental tool mounting said tool by friction pressure such that said tool is rotatable on said sleeve by finger pressure,

c. said first switch means has a first switch secured with said mount means,

d. said second switch means has a second switch secured with said mount means, and

e. said mount means has means to connect said first switch and said second switch to said battery and to said motor.

' '14. The dental instrument of claim 13, wherein:

a. said sleeve member is removably mountable with said handle,

b. said sleeve member is slidably engagable in an annular portion of said rotary dental tool,

0. said'mount means has an outer member adjacent said sleeve member with said first switch and said second switch secured therewith, and

d. said means to connect said first switch and said second switch each has a pair of contacts secured 

1. A portable dental instrument, comprising: a. a hollow handle, b. an electric motor mounted in said handle, said electric motor having a power output shaft, c. means to power said electric motor mounted in said handle and connected to said motor, d. speed changing means mounted on said handle and connected to said electric motor output shaft, said speed changing means, having an output shaft, and e. rotary dental tool mounting means for removably mounting a rotary dental tool in operating position, mounted on said speed changing means, and connected to said rotary dental tool when mounted to change the operating speed of said tool relative the operating speed of said motor, said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool and a sleeve member slidably engagable with said rotary dental tool and mounting said tool by friction pressure such that said tool is rotatable on said sleeve by finger pressure.
 2. The dental instrument of claim 1, wherein: a. said speed changing means has means to operate said rotary dental tool at a rotating speed different from the rotating speed of said motor output shaft, b. said means to power has a rechargeable battery and means to connect said battery with a battery charger means for recharging same said battery, and c. a motor control switch is mounted with said hand-piece and connected with said motor and said battery.
 3. A dental instrument of claim 2, wherein: a. said speed changing means has a first pulley secured to said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys.
 4. The dental instrument of claim 3, wherein: a. said sleeve member is removably mountable with said handle, b. said sleeve member is slidably engagable in an annular mount portion of said rotary dental tool, c. said motor is mounted in said handle in a position generally aligning with said battery, d. said means to connect said battery with a battery charger is an induction coil means, and e. said speed changing means is constructed and adapted to operate said rotary dental tool at a rotating speed lesser than the rotating speed of said motor, with said second pulley being larger than said first pulley.
 5. The dental instrument of claim 1, wherein: a. said speed changing means has means to rotate said rotary dental tool at a speed different than the rotating speed of said motor output shaft, b. said means to power has a rechargable battery and means to connect said battery with a battery charger means for recharging, and c. said means to power has a pair of parallely connected control switches, one switch mounted with said handle and a second switch mounted with said rotary dental tool mount means.
 6. The dental instrument of claim 5, wherein: a. said speed changing means has a first pulley secured said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys, b. said mount means has means to connect said second switch with said motor and said battery, and c. said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool, and a sleeve member slidably engagable with said rotary dental tool mounting said tool by friction pressure such that said tool is rotatable on said sleeve by finger pressure.
 7. The dental instrument of claim 6, wherein: a. said sleeve member is removably mountable with said handle, b. said sleeve member is of a diameter to be slidably engagable in an annular portion of said rotary dental tool, c. said mount means has an outer member secured to said sleeve member and mounting said second switch, d. said means to connect said second switch has one pair of contacts secured to said hand-piece and a second pair of contacts secured to said outer member, said pairs of contacts being cooperatively engagable when said outer member is mounted with said handle.
 8. The dental instrument of claim 3, wherein: a. said sleeve member is removably mountable with said handle, b. said sleeve member is of a size to be slidably engAgable in an annular mount portion of said rotary dental tool, c. said motor is mounted in said handle in a juxtapositional relation to said battery, and d. said output shaft is positioned with said rotatable axis thereof in a spaced relation to said motor and generally aligning with said battery.
 9. The dental instrument of claim 8, wherein: a. said output shaft is positioned with said rotatable axis parallel to said motor and in the space adjacent an end portion of said battery, and b. said means to power has a battery recharger means mounted in said handle connected to said battery and connectable to a source of electrical power.
 10. The dental instrument of claim 2, wherein said speed changing means has a first pulley secured to said motor output shaft, a rotatably mounted intermediate shaft having a second pulley and a third pulley secured therewith, said output shaft having a forth pulley secured therewith, a first drive belt therearound said first pulley and said second pulley and a second drive belt around said third pulley and said fourth pulley.
 11. The dental instrument of claim 10, wherein: a. said intermediate shaft is mounted in a spaced relation to said motor, and b. said output shaft is mounted in a spaced relation to said intermediate shaft and generally aligning with said motor.
 12. The dental instrument of claim 1, wherein: a. said speed changing means has means to rotate said rotary dental tool at a speed different than the rotating speed of said motor output shaft, b. said means to power has a rechargable battery and means to connect said battery with a battery charger means for recharging, c. said battery has a first power cell and a second power cell, and d. said means to power has a first switch means connected to said first power cell and to said motor and a second switch means connected to said first power cell, to said second power cell and to said motor in a series relation.
 13. The dental instrument of claim 12, wherein: a. said speed changing means has a first pulley secured to said motor output shaft, a second pulley secured to said output shaft and a drive belt therearound said pulleys, b. said mount means has a resilient coupler member connectable between said output shaft and a drive shaft of said rotary dental tool, and a sleeve member slidably engagable with said rotary dental tool mounting said tool by friction pressure such that said tool is rotatable on said sleeve by finger pressure, c. said first switch means has a first switch secured with said mount means, d. said second switch means has a second switch secured with said mount means, and e. said mount means has means to connect said first switch and said second switch to said battery and to said motor.
 14. The dental instrument of claim 13, wherein: a. said sleeve member is removably mountable with said handle, b. said sleeve member is slidably engagable in an annular portion of said rotary dental tool, c. said mount means has an outer member adjacent said sleeve member with said first switch and said second switch secured therewith, and d. said means to connect said first switch and said second switch each has a pair of contacts secured said outer member and another portion of each contacts secured to said handle, said pairs of contacts being cooperatively engagable when said outer member is mounted with said handle.
 15. The dental instrument of claim 1, wherein, said speed changing means is constructed to rotate said rotary dental tool at a speed lesser than said motor output shaft.
 16. The dental instrument of claim 1, wherein, said speed changing means is constructed to rotate said rotary dental tool at a speed greater than said motor output shaft. 